Powertrain fault management

ABSTRACT

A computer is programmed to determine an occupancy status of a vehicle based on received sensor data; and adjust a parameter of a powertrain of the vehicle in response to data indicating a critical condition of the powertrain based on the occupancy status. The parameter may be one of engine speed, cylinder deactivation, transmission-shift time, and shift schedule.

BACKGROUND

A vehicle powertrain typically includes an engine, a torque converter,and a transmission coupled in series, as well as a differential axle andsometimes a 4-wheel-drive transfer case. If the engine is aninternal-combustion engine, the engine includes cylinders that serve ascombustion chambers that convert fuel to rotational kinetic energy. Thetorque converter transmits rotational motion from the engine to thetransmission while allowing slippage between the engine andtransmission, for example, while the engine is running and the vehicleis stopped. The transmission transmits the kinetic energy from thetorque converter to a drive axle and ultimately to wheels of thevehicle, while applying a gear ratio allowing different tradeoffsbetween torque and rotational speed. Overheating and other faults cancause the powertrain to malfunction and/or damage the powertrain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an example vehicle.

FIG. 2 is a block diagram of the vehicle.

FIG. 3 is a process flow diagram of an example process for controllingpowertrain output.

FIG. 4 is a process flow diagram of an example process for planning aroute based on powertrain conditions.

FIG. 5 is a process flow diagram of an example process for adjustingpowertrain parameters based on powertrain conditions.

DETAILED DESCRIPTION

In response to overheating and other faults, operability of thepowertrain may need to be limited. The vehicle described below providesa system for responding to powertrain malfunctions and overheating inway that balances continued operability of the powertrain and theexperience of vehicle occupants, if any. A system includes a computerand powertrain components in communication with the computer. Thecomputer instructs the powertrain components to modify powertrainoperation in a manner that can prolong complete failure of thepowertrain without overly burdening occupants with noise, vibration, andharshness. The system can increase the likelihood that the vehiclereaches its destination without damaging the powertrain.

A system including a computer programmed to determine an occupancystatus of a vehicle based on received sensor data, and adjust aparameter of a powertrain of the vehicle in response to data indicatinga critical condition of the powertrain based on the occupancy status.

The parameter may be one of engine speed, cylinder deactivation,transmission-shifting speed, and shift schedule.

The occupancy status may be one of an occupied status and an unoccupiedstatus. The parameter may be engine speed, and the computer may befurther programmed to, in response to the data indicating the criticalcondition of the powertrain, increase the engine speed more for theunoccupied status than for the occupied status.

The parameter may be cylinder deactivation, and the computer may befurther programmed to, in response to the data indicating the criticalcondition of the powertrain, increase cylinder deactivation more for theunoccupied status than for the occupied status.

The parameter may be transmission-shift time, and the computer may befurther programmed to, in response to the data indicating the criticalcondition of the powertrain, decrease the transmission-shift time morefor the unoccupied status than for the occupied status.

The parameter may be threshold to shift of a shift schedule, and thecomputer may be further programmed to, in response to the dataindicating the critical condition of the powertrain, adjust thethreshold to shift of the shift schedule to increase lugging more forthe unoccupied status than for the occupied status.

The critical condition may be a temperature of the powertrain exceedinga temperature threshold. The computer may be further programmed todetermine the temperature threshold based on an ambient temperature.

A method includes determining an occupancy status of a vehicle based onreceived sensor data, and adjusting a parameter of a powertrain of thevehicle in response to data indicating a critical condition of thepowertrain based on the occupancy status.

The parameter may be one of engine speed, cylinder deactivation,transmission-shifting speed, and shift schedule.

The occupancy status may be one of an occupied status and an unoccupiedstatus. The parameter may be engine speed, and the method may furtherinclude, in response to the data indicating the critical condition ofthe powertrain, increasing the engine speed more for the unoccupiedstatus than for the occupied status.

The parameter may be cylinder deactivation, and the method may furtherinclude, in response to the data indicating the critical condition ofthe powertrain, increasing cylinder deactivation more for the unoccupiedstatus than for the occupied status.

The parameter may be transmission-shift time, and the method may furtherinclude, in response to the data indicating the critical condition ofthe powertrain, decreasing the transmission-shift time more for theunoccupied status than for the occupied status.

The parameter may be a threshold to shift of a shift schedule, and themethod may further include, in response to the data indicating thecritical condition of the powertrain, adjusting the threshold of theshift schedule to increase lugging more for the unoccupied status thanfor the occupied status.

The critical condition may be a temperature of the powertrain exceedinga temperature threshold. The method may include determining thetemperature threshold based on an ambient temperature.

With reference to FIGS. 1 and 2, a vehicle 30 may be an autonomousvehicle. A computer 32 can be configured to operate the vehicle 30independently of the intervention of a human driver, completely or to alesser degree. The computer 32 may be programmed to operate a propulsion34, brake system 36, steering 38, and/or other vehicle systems. For thepurposes of this disclosure, autonomous operation means the computer 32controls the propulsion 34, brake system 36, and steering 38;semi-autonomous operation means the computer 32 controls one or two ofthe propulsion 34, brake system 36, and steering 38 and a human drivercontrols the remainder; and nonautonomous operation means the humandriver controls the propulsion 34, brake system 36, and steering 38.

With reference to FIG. 1, the vehicle 30 includes a passenger cabin 40to house occupants, if any, of the vehicle 30. The passenger cabin 40includes one or more seats 42 disposed in a first row at a front of thepassenger cabin 40 and in a second row behind the first row. Thepassenger cabin 40 may also include seats 42 in a third row (not shown)at a rear of the passenger cabin 40. The position and orientation of theseats 42 and components thereof may have a different arrangement and/orbe adjustable by an occupant.

With reference to FIG. 2, the computer 32 is a microprocessor-basedcomputer. The computer 32 includes a processor, memory, etc. The memoryof the computer 32 includes memory for storing instructions executableby the processor as well as for electronically storing data and/ordatabases. The computer 32 may be a single computer or multiplecomputers networked together. For example, the computer 32 may includedistinct electronic control units (ECUs) or the like, e.g., a powertraincontrol module (PCM) and an autonomous-vehicle control module (AVCM), incommunication with each other.

The computer 32 may transmit signals through a communications network 44such as a controller area network (CAN) bus, Ethernet, WiFi, LocalInterconnect Network (LIN), onboard diagnostics connector (OBD-II),and/or by any other wired or wireless communications network. Thecomputer 32 may be in communication with the brake system 36, thesteering 38, components of the propulsion 34, AV sensors 46, occupancysensors 48, a transceiver 50, a powertrain thermometer 52, a towattachment 54, and other components.

The AV sensors 46 may provide data about operation of the vehicle 30,for example, wheel speed, wheel orientation, and engine and transmissiondata (e.g., temperature, fuel consumption, etc.). The AV sensors 46 maydetect the location and/or orientation of the vehicle 30. For example,the AV sensors 46 may include global positioning system (GPS) sensors;accelerometers such as piezo-electric or microelectromechanical systems(MEMS); gyroscopes such as rate, ring laser, or fiber-optic gyroscopes;inertial measurements units (IMU); and magnetometers. The AV sensors 46may detect the external world, i.e., phenomena outside the vehicle 30.For example, the sensors may include radar sensors, scanning laser rangefinders, light detection and ranging (LIDAR) devices, and imageprocessing sensors such as cameras.

The AV sensors 46 may include an external thermometer 56 to measure anambient temperature, i.e., a temperature of surrounding air of theexternal environment. The external thermometer 56 may be any suitabletype, e.g., magnetic, bimetallic strip, etc. The external thermometer 56may be disposed at any location at which the external thermometer 56 canachieve thermal equilibrium with the external environment.

The occupancy sensors 48 are configured to detect occupancy of the seats42. The occupancy sensors 48 may be visible-light or infrared camerasdirected at the seats 42, weight sensors inside the seats 42, sensorsdetecting whether seatbelts for the seats 42 are buckled or unspooled, ahuman-machine interface (HMI) allowing input from an occupant that theoccupant is present, or other suitable sensors.

The transceiver 50 is adapted to transmit signals wireles sly throughany suitable wireless communication protocol, such as Bluetooth®, WiFi,IEEE 802.11a/b/g, other RF (radio frequency) communications, etc. Thetransceiver 50 may be adapted to communicate with a remote server, thatis, a server distinct and spaced from the vehicle 30. The remote servermay be located outside the vehicle 30. For example, the remote servermay be associated with other vehicles (e.g., V2V communications),infrastructure components (e.g., V2I communications), emergencyresponders, mobile devices associated with the owner of the vehicle 30,etc. The transceiver 50 may be one device or may include a separatetransmitter and receiver.

The steering 38 is typically a known vehicle steering subsystem andcontrols the turning of vehicle 30 wheels of the vehicle 30. Thesteering 38 may be a rack-and-pinion system with electric power-assistedsteering, a steer-by-wire system, as both are known, or any othersuitable system. The steering 38 can include an electronic control unit(ECU) or the like that is in communication with and receives input fromthe computer 32 and/or a human driver. The human driver may control thesteering 38 via, e.g., a steering wheel.

With continued reference to FIG. 2, the brake system 36 is typically aknown vehicle braking subsystem and resists the motion of the vehicle 30to thereby slow and/or stop the vehicle 30. The brake system 36 mayinclude friction brakes such as disc brakes, drum brakes, band brakes,etc.; regenerative brakes; any other suitable type of brakes; or acombination. The brake system 36 can include an electronic brake controlunit (BCU) or the like that is in communication with and receives inputfrom the computer 32 and/or a human driver. The human driver may controlthe brake system 36 via, e.g., a brake pedal.

With reference to FIGS. 1 and 2, the propulsion 34 of the vehicle 30generates energy and translates the energy into motion of the vehicle30. The propulsion 34 includes a powertrain 58, which may include anengine 60 and a transmission 62 rotatably coupled to the engine 60. Thepropulsion 34 may be a known vehicle propulsion subsystem; for example,the powertrain 58 may include the engine 60 using internal combustioncoupled to the transmission 62 that transfers rotational motion towheels; may be electric and include batteries, an electric motor, andthe transmission 62 that transfers rotational motion to the wheels; maybe hybrid and include internal-combustion and electric elements; or maybe any other type of propulsion. The propulsion 34 can include anelectronic control unit (ECU) or the like that is in communication withand receives input from the computer 32 and/or a human driver. Theengine 60, transmission 62, etc., may be in communication with thecomputer 32 directly or via the ECU. A human driver may control thepropulsion 34 via, e.g., an accelerator pedal and/or a gear-shift lever.

The engine 60 may be an internal-combustion engine, an electric motor,or both. In an internal-combustion or hybrid engine, the engine 60includes a plurality of cylinders 64. The cylinders 64 operate ascombustion chambers in which a chemical reaction of a fuel translatesinto kinetic energy of a piston (not shown) of the cylinder 64. Thepistons of the cylinders 64 are coupled to the transmission 62 such thatlinear movement of the pistons drives rotational motion of thetransmission 62. The pistons may be coupled directly or indirectly,e.g., via a torque converter 66. The cylinders 64 of the engine 60 firein a predefined sequence.

The engine 60 has an engine speed. The engine speed is measured as arate of revolutions, e.g., revolutions per minute (rpm), of an outputshaft (not shown) coupled to the transmission 62. The strokes of thepistons drive the shaft. Changing the rate of piston firing changes theengine speed.

The engine 60 may use all the cylinders 64 to power the vehicle 30 ormay use a set of active cylinders 64 including less than all thecylinders 64. For example, if the engine 60 has six cylinders 64, thenall six cylinders 64 may fire in a sequence, four cylinders 64 may firein a sequence, three cylinders 64 may fire in a sequence, or some othernumber of cylinders 64 may fire in a sequence. The number of cylinders64 firing affects the noise, vibration, and harshness (NVH) experiencedby occupants of the vehicle 30, if any. For example, depending on theconfiguration of the engine 60, firing fewer than all the cylinders 64increases the NVH for occupants compared to firing all the cylinders 64,and firing an odd number of cylinders 64 increases the NVH for theoccupants compared to firing an even number of cylinders 64.

With continued reference to FIGS. 1 and 2, the transmission 62 iscoupled to the output shaft of the engine 60, that is, directly orindirectly drivably connected to the engine 60. The transmission 62transmits power generated by the engine 60 to a drive axle connected towheels (not shown). The transmission 62 can change the gear ratiobetween input from the engine 60 and output to the drive axle. Thetransmission 62 may be any suitable type of transmission 62, includingan automatic transmission with a set of defined gear ratios, calledgears, or a continuously variable transmission. At higher gear ratios orlower gears, the transmission 62 transmits more torque at a higherengine speed to the drive axle, and at lower gear ratios or highergears, the transmission 62 receives torque from the engine 60 at aslower engine speed for a given speed of the drive axle and transmitsless torque to the drive axle.

The transmission 62 can shift between gears. The transmission 62includes a plurality of physical gears engaged with one another, and ahydraulic system including a pump (not shown), as is known. Thehydraulic system changes the engagements of the physical gears, whichchanges the gear (e.g., from first to second). Transmission-shift time,for the purposes of this disclosure, refers to the time from when thetransmission 62 begins the transition to disengage from one gear, e.g.,first, to when the transmission 62 completes the engagement in anothergear, e.g., second. Increasing the pressure of the hydraulic systemdecreases the transmission-shift time, i.e., lowers the time for thetransmission 62 to shift gears, as well as increasing NVH.

A shift schedule may determine the gear ratio of the transmission 62 asa function of the vehicle speed and the position of an accelerator pedal(not shown). For an automatic transmission, a shift schedule indicatesthe conditions under which the transmission 62 will shift between twogears. The shift schedule may be represented as a series of thresholdsfor shifting between pairs of consecutive gears, and the thresholds arefunctions of the vehicle speed, the pedal position or some other measureof desired vehicle demand (such as an output of an autonomous-drivingalgorithm), and whether the shift is an upshift or downshift. The pedalis an input device, such as a floor pedal, through which an occupantindicates a desired change in the vehicle acceleration or speed.Lugging, for the purposes of this disclosure, means that thetransmission 62 delivers demanded torque at a lower engine speed and/orhigher gear than normally dictated by the shift schedule. Lugging mayresult in increased NVH such as vibrations being experienced by anoccupant.

With reference to FIG. 2, one or more powertrain thermometers 52 areattached to the powertrain 58 to monitor whether the powertrain 58 isoperating at a safe temperature. The powertrain thermometer 52 may beany suitable type, e.g., magnetic, bimetallic strip, etc. The powertrainthermometer 52 may be disposed at any location at which a temperaturereading correlates with operability of the powertrain 58. For example,the powertrain thermometer 52 may be located so that coolant exiting acylinder head or upper radiator hose (not shown) flows over thepowertrain thermometer 52.

With reference to FIGS. 1 and 2, the vehicle 30 may include the towattachment 54 for attaching a trailer to the vehicle 30. The towattachment 54 provides a structure to which the trailer can releasablyattach. The tow attachment 54 may be operable to couple to and releasefrom the trailer. Alternatively, the tow attachment 54 may be located onthe trailer and in communication with the computer 32 via a wiredconnection or wireless connection through the transceiver 50. The towattachment 54 on the trailer may be operable to couple to and releasefrom a structure of the vehicle 30. Alternatively, the tow attachment 54may be manually operable by an occupant of the vehicle 30.

FIG. 3 is a process flow diagram illustrating an exemplary process 300for controlling output of the powertrain 58. The memory of the computer32 stores programming for performing the steps of the process 300.

The process 300 begins in a block 305, in which the computer 32 receivesan ambient temperature. The external thermometer 56 detects the ambienttemperature and transmits a signal through the communications network 44to the computer 32.

Next, in a block 310, the computer 32 determines a first temperaturethreshold and a second temperature threshold. (The adjectives “first”and “second” are used throughout this document as identifiers and arenot intended to signify importance or order.) The temperature thresholdsmay be preset values, and the computer 32 may look up the temperaturethresholds in its memory. Alternatively, the temperature thresholds maybe based on the ambient temperature. For example, the temperaturethresholds may each be an increasing function of the ambienttemperature, e.g., T₁=a₁×T_(amb)+b₁ and T₂=a₂×T_(amb)+b₂, in which T₁ isthe first temperature threshold; T₂ is the second temperature threshold;T_(amb) is the ambient temperature; and a₁, b₁, a₂, and b₂ areconstants. The constants a₁, b₁, a₂, and b₂ may be determined byexperiments in which engines are run in high-ambient-temperatureenvironments to determine failure conditions. For another example,values of the temperature thresholds may be stored in lookup tables withcorresponding values of the ambient temperature. The values of thetemperature thresholds for each value of the ambient temperature may bedetermined by experiments in which engines are run inhigh-ambient-temperature environments to determine failure conditions.The second temperature threshold is greater than the first temperaturethreshold; more specifically, if the temperature thresholds are based onthe ambient temperature, the second temperature threshold is greaterthan the first temperature threshold for each value of the ambienttemperature.

Next, in a block 315, the computer 32 receives a temperature of thepowertrain 58. The powertrain thermometer 52 detects the powertraintemperature and transmits a signal through the communications network 44to the computer 32.

Next, in a decision block 320, the computer 32 determines whether it hasreceived data indicating a critical condition of the powertrain 58. Thecritical condition may be that the temperature of the powertrain 58exceeds the first temperature threshold, in other words, that thepowertrain 58 is overheating. If the temperature of the powertrain 58does not exceed the first temperature threshold, the process 300 returnsto the block 315; that is, the computer 32 continues to monitor thetemperature of the powertrain 58.

If the temperature of the powertrain 58 exceeds the first temperaturethreshold, next, in a decision block 325, the computer 32 determineswhether the temperature of the powertrain 58 exceeds the secondtemperature threshold. If the temperature of the powertrain 58 exceedsthe second temperature threshold, the process 300 proceeds to a block335.

If the temperature of the powertrain 58 does not exceed the secondtemperature threshold, next, in a block 330, the computer 32 caps thepower provided by the powertrain 58 to a first power limit. The firstpower limit may be a preset power value, measured in units of energy pertime, e.g., horsepower, watts, etc. Alternatively, the first power limitmay be a fraction less than one of power demanded from the powertrain58, e.g., 90%. The first power limit may be determined experimentally,e.g., by an experiment to determine what power level typically allowsthe powertrain 58 with a temperature between the first and secondtemperature thresholds to continue operating.

If the temperature of the powertrain 58 exceeds the second temperaturethreshold, in the block 335, the computer 32 caps the power provided bythe powertrain 58 to a second power limit. The second power limit may bea preset power value that is lower than the preset value of the firstpower limit. Alternatively, the second power limit may be a fractionless than one of power demanded from the powertrain 58 that is less thanthe fraction of the first power limit, e.g., 75%. The second power limitmay be determined experimentally, e.g., by an experiment to determinewhat power level typically allows the powertrain 58 with a temperatureabove the second temperature threshold to continue operating.

After the block 330 or the block 335, in a block 340, the computer 32receives an acceleration demand. “Acceleration demand,” for the purposesof this disclosure, refers to an instruction to the propulsion 34 for alevel of acceleration, whether the instruction includes a value ofacceleration or implicitly requests acceleration, e.g., by requesting anincreased value of speed. The acceleration demand may be generated by,e.g., an autonomous-driving algorithm, as is known, based on drivingconditions such as surrounding environment, other vehicles and objects,rules of the road, etc.

Next, in a decision block 345, the computer 32 determines whether theacceleration demand is above an acceleration threshold. The accelerationthreshold may be a value stored in the memory of the computer 32. Theacceleration threshold may be determined to correspond to driving eventsfor which higher acceleration is demanded, such as taking an onramp ontoa freeway, completing a pass of another vehicle, avoiding an incomingvehicle, etc. If the acceleration demand does not exceed theacceleration threshold, the process 300 proceeds to a block 355.

If the acceleration demand exceeds the acceleration threshold, next, ina decision block 350, the computer 32 determines whether theacceleration demand exceeds an energy limit. The energy limit, for thepurposes of this disclosure, is a total quantity of energy above thefirst or second power limit that the powertrain 58 is allowed to supply.The energy limit may be a value, e.g., a measurement in units of energysuch as Joules, stored in the memory of the computer 32. The energylimit may be determined by experiment, e.g., by an experiment todetermine a total energy above the power limit that the powertrain 58can typically supply while continuing to operate without causing damageto the life of the powertrain 58. If the acceleration demand wouldexceed the energy limit, the process 300 proceeds to a block 360.

If the acceleration demand does not exceed the acceleration threshold,after the decision block 345, or if the acceleration demand would notexceed the energy limit, after the decision block 350, in the block 355,the computer 32 provides power from the powertrain 58 even if the powerexceeds the first or second power limit (as instituted in the block 330or the block 335). After the block 355, the process 300 returns to theblock 315.

If the acceleration demand would exceed the energy limit, after thedecision block 350, in the block 360, the computer 32 caps the powerprovided by the powertrain 58 above the first or second power limit tothe energy limit. If the energy limit has already been exceeded, thecomputer 32 caps the power provided by the powertrain 58 to the first orsecond power limit. If the energy limit will be exceeded by theacceleration demand, the computer 32 allows the powertrain 58 to providepower above the first or second power limit up to the energy limit butthen caps the power provided by the powertrain 58 to the first or secondpower limit. After the block 360, the process 300 returns to the block315.

FIG. 4 is a process flow diagram illustrating an exemplary process 400for planning a route based on powertrain conditions. The memory of thecomputer 32 stores programming for performing the steps of the process400. In the process 400, the vehicle 30 is a first vehicle 30 in aplatoon that includes one or more second vehicles 90. (“First” and“second” do not necessarily refer to arrangement within the platoon.) A“platoon” is a group of vehicles 30, 90 that are traveling together in acoordinated manner (e.g., with respect to speed, heading, etc.). Thevehicles 30, 90 may be in communication with each other via thetransceiver 50 (as shown in FIG. 2) and may form a wireless ad hocnetwork using a dedicated short-range communications (DSRC) standardsand protocols. The vehicles 30, 90 may send message about impendingobstacles, traffic signals, etc.; intended actions; and so on. Thevehicles 30, 90 in the platoon may coordinate maneuvers such as brakingover the ad hoc network. The communication and coordination of maneuverssuch as braking allows the vehicles 30, 90 to travel more closelytogether than vehicles that are not in a platoon.

The process 400 begins in a block 405, in which the computer 32 receivesa request for a route to a destination. The request may be received via,e.g., user input.

Next, in a block 410, the computer 32 plans a first route to thedestination. The computer 32 may use a route-planning algorithm such asDijkstra's algorithm, A*, D*, and others, as are known, to generate thefirst route. The algorithm may minimize travel time, travel distance,etc.

Next, in a block 415, the computer 32 receives an ambient temperature.The external thermometer 56 detects the ambient temperature andtransmits a signal through the communications network 44 to the computer32.

Next, in a block 420, the computer 32 determines a temperaturethreshold. The temperature threshold may be a preset value, and thecomputer 32 may look up the temperature threshold in its memory.Alternatively, the temperature threshold may be based on the ambienttemperature. For example, the temperature threshold may be an increasingfunction of the ambient temperature, e.g., T=a×T_(amb)+b, in which T isthe temperature threshold; T_(amb) is the ambient temperature; and a andb are constants. The constants a and b may be determined by experimentsin which engines are run in high-ambient-temperature environments todetermine failure conditions. For another example, values of thetemperature threshold may be stored in lookup tables with correspondingvalues of the ambient temperature. The values of the temperaturethreshold for each value of the ambient temperature may be determined byexperiments in which engines are run in high-ambient-temperatureenvironments to determine failure conditions.

Next, in a block 425, the computer 32 receives a temperature of thepowertrain 58. The powertrain thermometer 52 detects the powertraintemperature and transmits a signal through the communications network 44to the computer 32.

Next, in a decision block 430, the computer 32 determines whether it hasreceived data indicating a critical condition of the powertrain 58. Thecritical condition may be that the temperature of the powertrain 58exceeds the temperature threshold, in other words, that the powertrain58 is overheating. If the temperature of the powertrain 58 does notexceed the temperature threshold, the process 400 returns to the block425; that is, the computer 32 continues to monitor the temperature ofthe powertrain 58.

If the temperature of the powertrain 58 exceeds the temperaturethreshold, next, in a block 435, the computer 32 instructs the firstvehicle 30 to pull over. For example, the computer 32 may use theautonomous-driving algorithm to instruct the propulsion 34, steering 38,and brake system 36 to move the first vehicle 30 to a shoulder or sideof a road on which the first vehicle 30 is driving and to slow and stopthe first vehicle 30.

Next, in a block 440, the computer 32 receives map data and trafficdata. The map data is typically conventional map data as provided in avehicle navigation system and typically includes data about roadlocations and lengths, local traffic regulations for the roads,topographical data, etc. The computer 32 may receive the map data viathe transceiver 50 or by looking up the map data from the memory. Thetraffic data can include for a particular road or a segment (e.g., onemile, two miles) of a road, a number of vehicles of the road, averagespeeds of vehicles on the road or road segment, delays if any, etc.

Next, in a block 445, the computer 32 generates a plurality of possibleroutes from a current location of the first vehicle 30 to thedestination. The computer 32 may generate the possible routes in theprocess of using a route-planning algorithm such as Dijkstra'salgorithm, A*, D*, and others, as are known.

Next, in a block 450, the computer 32 calculates a metric of exertion bythe powertrain 58 for the possible routes based on the map data and thetraffic data. “Metric of exertion,” for the purposes of this disclosure,is a value representing how hard the powertrain 58 will work whiletraversing the route. The metric of exertion may be a total value forthe route, an average value over the route, or a peak value over theroute. The metric of exertion may be, e.g., energy consumption, averagepower consumption, average heat generation rate, peak power consumption,etc. For example, “predicted energy consumption,” for the purposes ofthis disclosure, is an estimation by the computer 32 of an amount ofenergy that the powertrain 58 will expend for the first vehicle 30 totraverse a route. The predicted energy consumption is measured in unitsof energy such as Joules. The computer 32 may calculate the predictedenergy consumption by estimating how much acceleration the first vehicle30 will likely use to traverse each of the possible routes, based onintersections at which the first vehicle 30 will need to stop, speedlimits along segments of the possible route, uphill portions of thepossible route, etc. For example, the computer 32 may use this formula:

$E = {{\sum\limits_{l \in {\{{25,35,45,55,65}\}}}^{\;}\left( {{I_{l}E_{{acc}->l}} + {D_{l}E_{l}}} \right)} + {\sum\limits_{i = 1}^{N}{E_{grad}\left( g_{i} \right)}}}$in which l is a speed limit, I_(l) is a number of intersections on theroute at which the first vehicle 30 will stop before a section with aspeed limit l, E_(acc→l) is an amount of energy to accelerate up to aspeed l, D_(l) is a distance of the route with a speed limit l, E_(l) isan energy to maintain a speed l per unit distance, i is an index foreach mile (or another distance segment) along the route, N is a totalnumber of miles (or other distance segments) for the route, g_(i) is agradient (i.e., steepness, measured in e.g., angular units such asdegrees) at mile i, and E_(grad) is an additional energy to ascend agradient for the distance segment above the energy to travel on levelground for the distance segment. The terms E_(acc→l), E_(l), andE_(grad) may be based on experimental data gathered while driving thefirst vehicle 30. For another example, “average power consumption,” forthe purposes of this disclosure, is an estimation by the computer 32 ofan average power that the powertrain 58 will generate over the route.The average power consumption may be calculated, e.g., as the energyconsumption divided by an estimated travel time of the route.Alternatively, the average power consumption may be calculated as anaverage or root-mean-square of expected power consumptions at, e.g.,uniformly spaced points along the route. For another example, “averageheat generation rate,” for the purposes of the disclosure, is anestimation by the computer 32 of heat generated by the powertrain perunit distance or time along the route. The average heat generation ratemay be calculated using a similar formula with terms determined byexperimentation on how the powertrain 58 generates heat under differentdriving conditions, road environments, traffic scenarios, etc. Foranother example, “peak power consumption,” for the purposes of thisdisclosure, is an estimation by the computer 32 of a maximum power thatthe powertrain 58 will produce while traversing the route. The memory ofthe computer 32 may store power consumption scores for different drivingscenarios, and the computer 32 may calculate the peak power consumptionby determining which driving scenario occurring along the route has thehighest score. The computer 32 may calculate the metric of exertion ofthe possible routes in the process of using a route-planning algorithmsuch as Dijkstra's algorithm, A*, D*, and others, as are known.Specifically, the metric of exertion may be a metric optimized by theroute-planning algorithm or may be a component of a metric optimized bythe route-planning algorithm.

Next, in a block 455, the computer 32 selects a second route from amongthe possible routes that has the lowest metric of exertion (or theoptimized value of a metric including the metric of exertion) andmodifies the first route to the second route. The metric of exertion istherefore lower for the second route than for the first route.

Next, in a decision block 458, the computer 32 determines whether thefirst vehicle 30 is traveling as a member of a platoon. Membershipstatus in a platoon may be stored in the memory of the computer 32. Ifthe first vehicle 30 is not a member of a platoon, the process 400proceeds to a block 475.

If the first vehicle 30 is a member of a platoon, next, in a decisionblock 460, the computer 32 determines whether the first vehicle 30 istowing a trailer. For example, the computer 32 may determine whether thetow attachment 54 is attached. If the first vehicle 30 is not towing atrailer, the process 400 proceeds to a block 470.

If the first vehicle 30 is towing a trailer, next, in a block 465, thecomputer 32 instructs the tow attachment 54 to detach the trailer.Alternatively, a message may be transmitted to an occupant to detach thetrailer.

Next, or after the decision block 460 if the first vehicle 30 is nottowing a trailer, in the block 470, the computer 32 transmits a requestvia the transceiver 50 to one of the second vehicles 90 to follow thesecond route. If the first vehicle 30 was towing a trailer, the computer32 may also transmit a request that the second vehicle 90 tow thetrailer. The first vehicle 30 may move so that the second vehicle 90 hasspace to attach the trailer; for example, the first vehicle 30 may driveforward by a preset distance. The preset distance may be stored in thememory of the computer 32. The preset distance may be chosen based onproviding the second vehicle 90 sufficient space to parallel parkbetween the first vehicle 30 and the trailer.

Next, or after the decision block 458 if the first vehicle 30 is not ina platoon, in a block 475, the computer 32 instructs the first vehicle30 to begin following the second route. For example, the computer 32 mayuse the autonomous-driving algorithm to instruct the propulsion 34,steering 38, and brake system 36 to drive the first vehicle 30 along thesecond route. While doing so, the computer 32 may also implement theprocess 300 described above and/or the process 500 described below.

Next, in a block 480, while following the second route, the computer 32receives a number of vehicles following the first vehicle 30. The numberof following vehicles may exclude the second vehicles 90 in the platoonwith the first vehicle 30; in other words, the number of followingvehicles may include only vehicles unrelated to the platoon. Thecomputer 32 may receive data from the AV sensors 46 and interpret thedata to determine the number of following vehicles using known imageanalysis and/or other object-recognition techniques.

Next, in a decision block 485, the computer 32 determines whether thenumber of following vehicles exceeds a following-vehicle threshold,e.g., three. The following-vehicle threshold may be determined by userinput or may be a preset value. The preset value for thefollowing-vehicle threshold may be based on surveying customerpreference. If the number of following vehicles does not exceed thefollowing-vehicle threshold, the process 400 proceeds to a decisionblock 490.

If the number of following vehicles exceeds the following-vehiclethreshold, next, in a block 490, the computer 32 instructs the firstvehicle 30 to pull over until the following vehicles have passed thefirst vehicle 30. For example, the computer 32 may use theautonomous-driving algorithm to instruct the propulsion 34, steering 38,and brake system 36 to move the first vehicle 30 to a shoulder or sideof a road on which the first vehicle 30 is driving, slow and stop thefirst vehicle 30, wait until the following vehicles have passed, andaccelerate the first vehicle 30 back onto the road.

After the decision block 485, if the number of following vehicles doesnot exceed the following-vehicle threshold, or after the block 490, thecomputer 32 determines whether the first vehicle 30 has arrived at thedestination. The computer 32 may use, e.g., GPS data from the AV sensors46 to compare the location of the first vehicle 30 to the location ofthe destination. If the first vehicle 30 is not at the destination, theprocess 400 returns to the block 475 to continue following the secondroute. If the first vehicle 30 is at the destination, the process 400ends.

FIG. 5 is a process flow diagram illustrating an exemplary process 500for planning a route based on powertrain conditions. The memory of thecomputer 32 stores programming for performing the steps of the process500.

The process 500 begins in a block 505, in which the computer 32 receivessensor data from the occupancy sensors 48. The sensor data may be imagesfrom cameras directed at the seats 42, weight values from weight sensorsin the seats 42, binary signals from sensors detecting whether seatbeltsfor the seats 42 are buckled or unspooled, etc.

Next, in a block 510, the computer 32 determines an occupancy status ofthe vehicle 30 based on the sensor data. “Occupancy status,” for thepurposes of this disclosure, is a classification based on the presence,location, number, etc. of occupants in the passenger cabin 40. Forexample, the occupancy status may be one of an occupied status, i.e., atleast one occupant in the passenger cabin 40, and an unoccupied status,i.e., zero occupants in the passenger cabin 40. The computer 32 uses thesensor data to determine the occupancy status. For example, the computer32 may have object recognition algorithms to recognize an occupant inone of the seats 42 based on images from cameras by, e.g., comparing theimages to baseline images. For another example, the computer 32 mayreceive a weight above a weight threshold from at least one weightsensor in one of the seats 42. The weight threshold may be chosen to below enough that, e.g., 99% of a population of possible occupants areheavier. For another example, a binary signal from a sensor in at leastone seatbelt buckle indicates that the buckle is buckled.

Next, in a block 515, the computer 32 receives an ambient temperature.The external thermometer 56 detects the ambient temperature andtransmits a signal through the communications network 44 to the computer32.

Next, in a block 520, the computer 32 determines a temperaturethreshold, as described above with respect to the block 420 of theprocess 400.

Next, in a block 525, the computer 32 receives a temperature of thepowertrain 58. The powertrain thermometer 52 detects the powertraintemperature and transmits a signal through the communications network 44to the computer 32.

Next, in a decision block 530, the computer 32 determines whether it hasreceived data indicating a critical condition of the powertrain 58. Thecritical condition may be that the temperature of the powertrain 58exceeds the temperature threshold, in other words, that the powertrain58 is overheating. If the temperature of the powertrain 58 does notexceed the temperature threshold, the process 500 returns to the block525; that is, the computer 32 continues to monitor the temperature ofthe powertrain 58.

Next, in a block 535, the computer 32 determines the occupancy status.The occupancy status determined in the block 510 may be stored in thememory of the computer 32. If the occupancy status is the unoccupiedstatus, the process 500 proceeds to the block 545.

If the occupancy status is the occupied status, next, in a block 540,the computer 32 adjusts one or more parameters of the powertrain 58. Theparameters are values governing operation of the powertrain, andtypically include engine speed, cylinder deactivation,transmission-shift time, and threshold to shift of a shift schedule. Forexample, the computer 32 may increase the engine speed. A higher enginespeed can, in the event of a leak of coolant, pump more air through theengine 60 as a substitute coolant. The engine speed varies duringoperation of the vehicle 30, but the engine speed is increased beyond adefault value for any value of torque demanded from the engine. Foranother example, the computer 32 may increase cylinder deactivation,i.e., fire fewer cylinders 64 in the firing sequence, e.g., fourcylinders 64 instead of six cylinders 64. For another example, thecomputer 32 may decrease the transmission-shift time. The computer 32may, for example, increase the pressure in the hydraulic system for gearshifting. The time to shift gears may decrease, e.g., from 0.5 secondsto 0.3 seconds. For another example, the computer 32 may adjust thethreshold to shift of the shift schedule to increase lugging, i.e.,lowering the engine speed or raising the gear for a given demandedtorque. For a given acceleration demand, the threshold to shift may be afunction of speed of the vehicle 30 and whether the shift is an upshiftor a downshift. After the block 540, the process 500 ends.

If the occupancy status is the unoccupied status, in the block 545, thecomputer 32 adjusts one or more parameters of the powertrain 58 to amore extreme value than for the occupied status, i.e., than in the block540. The more extreme values may increase the NVH in the passenger cabin40, but the passenger cabin 40 does not contain occupants that wouldexperience the increased NVH. For example, the computer 32 may increasethe engine speed more for the unoccupied status than for the occupiedstatus. For another example, the computer 32 may increase they cylinderdeactivation more for the unoccupied status than for the occupiedstatus, e.g., three cylinders 64 instead of six cylinders 64. Foranother example, the computer 32 may decrease the transmission-shifttime more for the unoccupied status than for the occupied status, e.g.,from 0.5 seconds to 0.2 seconds, which may reduce friction heat createdduring the shift and that results in a larger NVH torque disturbance.For another example, the computer 32 may adjust the threshold to shiftof the shift schedule to increase lugging more for the unoccupied statusthan for the occupied status. After the block 545, the process 500 ends.

In general, the computing systems and/or devices described may employany of a number of computer operating systems, including, but by nomeans limited to, versions and/or varieties of the Ford Sync®application, AppLink/Smart Device Link middleware, the MicrosoftAutomotive® operating system, the Microsoft Windows® operating system,the Unix operating system (e.g., the Solaris® operating systemdistributed by Oracle Corporation of Redwood Shores, Calif.), the AIXUNIX operating system distributed by International Business Machines ofArmonk, N.Y., the Linux operating system, the Mac OSX and iOS operatingsystems distributed by Apple Inc. of Cupertino, Calif., the BlackBerryOS distributed by Blackberry, Ltd. of Waterloo, Canada, and the Androidoperating system developed by Google, Inc. and the Open HandsetAlliance, or the QNX® CAR Platform for Infotainment offered by QNXSoftware Systems. Examples of computing devices include, withoutlimitation, an on-board vehicle computer, a computer workstation, aserver, a desktop, notebook, laptop, or handheld computer, or some othercomputing system and/or device.

Computing devices generally include computer-executable instructions,where the instructions may be executable by one or more computingdevices such as those listed above. Computer executable instructions maybe compiled or interpreted from computer programs created using avariety of programming languages and/or technologies, including, withoutlimitation, and either alone or in combination, Java™, C, C++, Matlab,Simulink, Stateflow, Visual Basic, Java Script, Perl, HTML, etc. Some ofthese applications may be compiled and executed on a virtual machine,such as the Java Virtual Machine, the Dalvik virtual machine, or thelike. In general, a processor (e.g., a microprocessor) receivesinstructions, e.g., from a memory, a computer readable medium, etc., andexecutes these instructions, thereby performing one or more processes,including one or more of the processes described herein. Suchinstructions and other data may be stored and transmitted using avariety of computer readable media. A file in a computing device isgenerally a collection of data stored on a computer readable medium,such as a storage medium, a random access memory, etc.

A computer-readable medium (also referred to as a processor-readablemedium) includes any non-transitory (e.g., tangible) medium thatparticipates in providing data (e.g., instructions) that may be read bya computer (e.g., by a processor of a computer). Such a medium may takemany forms, including, but not limited to, non-volatile media andvolatile media. Non-volatile media may include, for example, optical ormagnetic disks and other persistent memory. Volatile media may include,for example, dynamic random access memory (DRAM), which typicallyconstitutes a main memory. Such instructions may be transmitted by oneor more transmission media, including coaxial cables, copper wire andfiber optics, including the wires that comprise a system bus coupled toa processor of a ECU. Common forms of computer-readable media include,for example, a floppy disk, a flexible disk, hard disk, magnetic tape,any other magnetic medium, a CD-ROM, DVD, any other optical medium,punch cards, paper tape, any other physical medium with patterns ofholes, a RAM, a PROM, an EPROM, a FLASH-EEPROM, any other memory chip orcartridge, or any other medium from which a computer can read.

Databases, data repositories or other data stores described herein mayinclude various kinds of mechanisms for storing, accessing, andretrieving various kinds of data, including a hierarchical database, aset of files in a file system, an application database in a proprietaryformat, a relational database management system (RDBMS), etc. Each suchdata store is generally included within a computing device employing acomputer operating system such as one of those mentioned above, and areaccessed via a network in any one or more of a variety of manners. Afile system may be accessible from a computer operating system, and mayinclude files stored in various formats. An RDBMS generally employs theStructured Query Language (SQL) in addition to a language for creating,storing, editing, and executing stored procedures, such as the PL/SQLlanguage mentioned above.

In some examples, system elements may be implemented ascomputer-readable instructions (e.g., software) on one or more computingdevices (e.g., servers, personal computers, etc.), stored on computerreadable media associated therewith (e.g., disks, memories, etc.). Acomputer program product may comprise such instructions stored oncomputer readable media for carrying out the functions described herein.

In the drawings, the same reference numbers indicate the same elements.Further, some or all of these elements could be changed. With regard tothe media, processes, systems, methods, heuristics, etc. describedherein, it should be understood that, although the steps of suchprocesses, etc. have been described as occurring according to a certainordered sequence, such processes could be practiced with the describedsteps performed in an order other than the order described herein. Itfurther should be understood that certain steps could be performedsimultaneously, that other steps could be added, or that certain stepsdescribed herein could be omitted. In other words, the descriptions ofprocesses herein are provided for the purpose of illustrating certainembodiments, and should in no way be construed so as to limit theclaims.

Accordingly, it is to be understood that the above description isintended to be illustrative and not restrictive. Many embodiments andapplications other than the examples provided would be apparent to thoseof skill in the art upon reading the above description. The scope of theinvention should be determined, not with reference to the abovedescription, but should instead be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. It is anticipated and intended that futuredevelopments will occur in the arts discussed herein, and that thedisclosed systems and methods will be incorporated into such futureembodiments. In sum, it should be understood that the invention iscapable of modification and variation and is limited only by thefollowing claims.

All terms used in the claims are intended to be given their plain andordinary meanings as understood by those skilled in the art unless anexplicit indication to the contrary in made herein. In particular, useof the singular articles such as “a,” “the,” “said,” etc. should be readto recite one or more of the indicated elements unless a claim recitesan explicit limitation to the contrary. Use of “in response to” and“upon determining” indicates a causal relationship, not merely atemporal relationship.

The disclosure has been described in an illustrative manner, and it isto be understood that the terminology which has been used is intended tobe in the nature of words of description rather than of limitation. Manymodifications and variations of the present disclosure are possible inlight of the above teachings, and the disclosure may be practicedotherwise than as specifically described.

What is claimed is:
 1. A system comprising a computer programmed to:determine an occupancy status of a vehicle based on received sensordata; adjust a cylinder deactivation of a powertrain of the vehicle inresponse to data indicating a critical condition of the powertrain basedon the occupancy status; and in response to the data indicating thecritical condition of the powertrain, increase cylinder deactivationmore for an unoccupied status than for an occupied status, wherein apositive number of cylinders are active for the unoccupied status andfor the occupied status.
 2. The system of claim 1, wherein the criticalcondition is a temperature of the powertrain exceeding a temperaturethreshold.
 3. The system of claim 2, wherein the computer is furtherprogrammed to determine the temperature threshold based on an ambienttemperature.
 4. A method comprising: determining an occupancy status ofa vehicle based on received sensor data; and adjusting a cylinderdeactivation of a powertrain of the vehicle in response to dataindicating a critical condition of the powertrain based on the occupancystatus; and in response to the data indicating the critical condition ofthe powertrain, increasing cylinder deactivation more for an unoccupiedstatus than for an occupied status, wherein a positive number ofcylinders are active for the unoccupied status and for the occupiedstatus.
 5. The method of claim 4, wherein the critical condition is atemperature of the powertrain exceeding a temperature threshold.
 6. Themethod of claim 5, further comprising determining the temperaturethreshold based on an ambient temperature.